you cannot be under 25 and use a debit card. you can do either or. Call the res center and tell them where you will be renting. They will look up the debit requirements for your location. Foriegn (non u.s. bank) debit cards will never be accepted at the beginning of the rental, but will be accepted at the end.
Depending on the region, debit cards will be holding 300+, meaning the minimum hold will be your estimated total, or the minimum, which ever is greater.
There are 2-3 regions around the nation which do not accept debit cards at all, but any manager, given the right situation, may waive it. But if a manager waives the card and allows it, and it gets turned back, the manager risks their job, so those willing to waive debits out of policy are few and far between. I only did it 3 times in 5 years before debit cards were allowed, all were individuals whom had ties to big accounts where I was sure I could track them down. Average joe schmo barely had a chance to get by me, lest I risk my job.